The present invention relates to a steel mold, especially made of highly heat-resistant hot casting steel for metal casting in permanent mold casting processes.
It is known to provide steel molds for aluminum casting with channels through which a cooling medium may flow in order to shorten the casting cycle and to prevent hot spots within the area of thicker portions of the molded material. These cooling channels, conventionally produced by providing bores in the rearward side of the massive steel mold are always positioned at a relatively great distance to the mold surface of at least 20 to 30 mm in order to prevent cracks and breakage due to thermally induced local tension.
Due to this relatively great distance of the cooling channels to the hot mold surface, only a small portion of the heat introduced into the mold by casting the liquid metal can be removed via the heat dissipation means through the steel mold so that during manufacture the heat dissipation is achieved mainly by spraying water directly onto the contour of the mold after opening the mold and removing the molded component. The resulting thermal tensions lead to fatigue cracks within the steel mold surface due to the use of the permanent mold for repeated casting cycles and thus a shortened service life of such a steel mold. In many cases already after 20,000 castings such a steel mold or a portion of the steel mold must be renewed.
It is therefore an object of the present invention to provide a permanent steel mold especially for mold casting metal, such as aluminum die-casting, with which the disadvantages of the known steel molds are eliminated, the risk of cracking of the steel mold is substantially reduced, and the time for each working cycle can be reduced by at least 30%.